Calculating Rent By Year

I have attached the spreadsheet in a pdf. I can e-mail it to anyone who is is willing to help me.

I am trying to calculate the amount of income per calendar year from each tenant.

I have, for each tenant, a commencement date (the date that the first lease year began) and a termination date (the date the last lease year ended). If a tenant has signed a 10 year lease, for example, and his lease commenced on February 15, 2005, then it will terminate on February 14, 2015. The 10 years in that range each have a different rent for that year. Year 1, (from February 15, 2005-February 14, 2006) he will pay $4k a month. In Year 2, (from February 15, 2005-February 14, 2006) he will pay $6k a month. What I want is a set of columns that show the total rent he will pay in 2005, 2006, and so on. The 2005 total should be: $42,000 (10.5*$4000). In 2006, it should be: $69,000 (1.5*4000 + 10.5*6000), and so on to year 10 (being split between 2014 and 2015. Also, please note that the lease could commence on any day of the month and they pay the corresponding pro-rata share of rent based on the number of days into the month the Lease Year is starting/changing.

The result should look like this:

[2005][2006]
[$42000][$69000]
next tenant amounts
next tenant amounts